This invention relates to brake mechanisms, and more particularly, to a brake mechanism including a booster system wherein air pressure may be applied to a piston to move the piston in addition to spring force being applied thereto.
In a system for braking a large vehicle, it is well-known to provide that the brakes thereof release upon application of fluid pressure thereto, and are applied by spring means associated with the brakes upon the release of such fluid pressure therefrom. In a typical parking brake arrangement for such a vehicle, the spring means apply the brakes of the vehicle upon selective release of such fluid pressure. In such a system, it may occur that the operator of the vehicle applies the parking brake in a manner described, and then inadvertently operates the vehicle with the parking brake still applied. With the relatively great power of the vehicle involved, it will be understood that it is indeed possible under certain circumstances to greatly wear such parking brake system.
The substance of the present invention relates to the application of force to the piston in a brake-applying direction, in addition to the spring force described above. U.S. Pat. No. 3,791,492 discloses a brake mechanism incorporating application of fluid pressure to and release of fluid pressure from certain chambers thereof. Such patent discloses the application of fluid pressure into a chamber wherein a spring is disposed. However, it will be noted that such spring force is overcome upon application of fluid pressure to such chamber, i.e. the pressure applied to the chamber does not provide force additional to the force of the spring to apply the brakes of the vehicle.